The objectives of this research are to elucidate the immunological and structural characteristics of nuclear poly(A) polymerase from a rapidly growing hepatoma and from normal rat liver, to investigate the response of the nucllar enzymes to altered physiological conditions, to study the regulation of the levels of this enzyme and finally to establish the role of this enzyme in controlling the polyadenylation of mRNA. Nuclear poly(A) polymerase will be purified from rat liver and Morris hepatoma 3924A by the procedures established in this laboratory (Rose, K.M. and Jacob, S.T., Eur. J. Biochem. 67, 11, 1976). Monospecific antibodies against the enzymes will be prepared and a highly sensitive radioimmunoassay for poly(A) polymerase will be developed. Using the radioimmunoassay and other immunological criteria, the antigenic relationship between the liver and tumor enzymes, between the enzymes in different cellular compartments, and between poly(A) polymerase and RNA polymerases will be determined. If the hepatoma enzyme is a cancer-specific antigen, development of radioimmunoassay may facilitate diagnosis of liver cancer in tissue samples removed for biopsy. Structural properties of liver and hepatoma nuclear poly(A) polymerases will be studied by performing N-terminal and C-terminal analyses and by peptide mapping. The regulation of the levels of poly(A) polymerase in response to amino acid supply will be investigated in rat liver and in rat hepatomas. Changes in the levels of enzyme protein in liver and hepatoma from normal, amino acid deprived and refed rats will be determined by radioimmunoassay. Alterations in the levels of mRNA for poly(A) polymerase under varying physiological and pathological conditions will be qualitatively assessed by translating total mRNAs in cell-free protein synthesizing systems. Attempts will be made to isolate pure poly(A) polymerase mRNA by the highly sensitive immunotechniques and to synthesis cDNA which can then be used to quantitatively determine the number of mRNA molecules of this enzyme under varying physiological conditions. Posttranslational modifications of nuclear poly(A) polymerase will also be investigated.